Archive for the ‘commissioning’ Category

A comment from Gert reveals the news that HIFI will be returning to operations in 2010. This is the third instrument on Herschel alongside SPIRE and PACS. It’s been suffering from technical difficulties which have been investigated for the last several months. A fix has now been determined and we hope that it will rapidly return to full operation once it’s been turned back on.

Things have been rather quiet of late. This isn’t because nothing is happening. Quite the opposite in fact – lots of work is being done to get the instruments fulling calibrated and their observing modes fully working.

Great progress is being made with our instrument, SPIRE, and lots of interesting things are being seen, but the scientists working on the instrument aren’t allowed to do science with the data being taken at the moment and anyway don’t have time to do it, since they’re hard at work getting the performance tests and calibration done.

Good things, very good things, are on their way though. The first public release of these will be in the middle of December once the initial science observations and the first steps of data analysis have been completed.

As well as the first light images from PACS and SPIRE, HIFI, the high resolution spectrometer on Herschel, also released its first light spectra last week.

This shows lines from ionized carbon, CO and water molecules within the cloud. These lines are totally inaccessible from beneath the Earth’s atmosphere so there have been few studies of them until now. The broad Carbon line at the position of a young, forming star shows the effects of the powerful winds streaming from the star’s surface. To be able to produce spectra so good from an instrument that has yet to be tuned and optimized is quite an achievement!

Since launch Herschel and its instruments have been going through a testing phase known as Commissioning. Essentially this means making sure everything still works after launch and making sure the whole system works as a whole. The next phase, called Performance Verification consists of much more detailed testing and calibration of the instruments to get them working at optimal performance and to establish all the calibration data needed for full scientific use.

Yesterday there was a review of all three instruments to determine their readiness to move from Commissioning Phase to Performance Verification Phase.

All three are ready to go, which places us one important step closer to real science with Herschel! I’m sure you’ll join me in congratulating the instrument teams on completing this phase successfully!

One of the key components of Herschel is its 3.5m primary mirror, the largest ever launched on an astronomical satellite. Because of its unfeasible size, the mirror was launched warm, at room temperature. Herschel operations require a much colder mirror – as cold as possible – since the sensitivity of the detectors is limited by the background thermal noise coming from the mirror. This is why Herschel has such a big sunshade, to keep the light of the sun and earth from heating up the mirror and other parts of the satellite, and ever since launch the primary mirror has been cooling by radiating its heat into space.

The final temperature the mirror reaches will be one of the determining factors in Herschel’s eventual sensitivity. The design requires it to reach about 80K, that’s 80 degrees above absolute zero, or -193 C. This plot shows how things are progressing:

For the long stable period form day 5 to day 23 the mirror was heated to keep it at a stable temperature while contaminant gasses were allowed to boil off. Since then the mirror has been cooling well and, as you can see, we’re already pretty close to the goal temperature.

PACS has seen first light, taking an image of the galaxy M51. I’ve not seen the image yet, it should be made public on Friday and I’m not allowed to see it before that, but the word is that it looks good, and the fast processed image is at least as good as the best images from Spitzer of this object.